According to New Horizons planetary scientists, this frozen region is no more than 100 million years old, and is possibly still being shaped by geologic processes.
This view of a portion of Pluto’s Sputnik Planum shows enigmatic features: the surface appears to be divided into irregularly shaped segments that are ringed by narrow troughs, some of which contain darker materials; features that appear to be groups of mounds and fields of small pits are also visible. This image was acquired on July 14 from a distance of 48,000 miles (77,000 km). Features as small as a half-mile (1 km) across are visible. Image credit: NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute.
This icy plains region, Sputnik Planum, is north of Pluto’s icy mountains, in the center-left of the heart feature, named Tombaugh Regio after Clyde Tombaugh, who discovered the dwarf planet in 1930.
“This terrain is not easy to explain. The discovery of vast, craterless, very young plains on Pluto exceeds all pre-flyby expectations,” said New Horizons team member Dr Jeff Moore of NASA’s Ames Research Center.
The region has a broken surface of irregularly-shaped segments, roughly 12 miles (20 km) across, bordered by what appear to be shallow troughs.
Some of these troughs have darker material within them, while others are traced by clumps of hills that appear to rise above the surrounding terrain.
Elsewhere, the surface appears to be etched by fields of small pits that may have formed by a process called sublimation, in which ice turns directly from solid to gas, just as dry ice does on Earth.
New Horizons scientists have two theories as to how these segments were formed.
The irregular shapes may be the result of the contraction of surface materials, similar to what happens when mud dries.
Alternatively, they may be a product of convection, similar to wax rising in a lava lamp. On Pluto, convection would occur within a surface layer of frozen carbon monoxide, methane and nitrogen, driven by the scant warmth of Pluto’s interior.
Pluto’s icy plains also display dark streaks that are a few miles long. These streaks appear to be aligned in the same direction and may have been produced by winds blowing across the frozen surface.
New Horizons researchers also said that the Ralph instrument aboard the spacecraft revealed evidence of carbon monoxide ice in the western half of Tombaugh Regio.
Frozen carbon monoxide in ‘heart of Pluto:’ the contours indicate that the concentration of frozen carbon monoxide increases towards the center of the ‘bull’s eye.’ Image credit: NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute.
“With the flyby in the rearview mirror, a decade-long journey to Pluto is over – but, the science payoff is only beginning. Data from New Horizons will continue to fuel discovery for years to come,” said Dr Jim Green of NASA Headquarters in Washington.
“We’ve only scratched the surface of our Pluto exploration, but it already seems clear to me that in the initial reconnaissance of the Solar System, the best was saved for last,” added Dr Alan Stern of the Southwest Research Institute, principal investigator for New Horizons.
